Sink-float test

There are different test methods available, which allow the characterization of the wicking behavior of fibrous assemblies, such as the canvas disk wetting test, the Draves test, the demand wetting test, and the Lennox-Kerr test or sinking float test. Kissa [101] reviewed these techniques and the theoretical basics of wetting and wicking of such fiber assemblies. Therefore we... 

The response of any given feed to sink-float processing can be accurately established in the laboratory by testing with various heavy hq-uids. The hquids generally used for this purpose are listed in Table 19-12. These halogenated hydrocarbons are mutually miscible, which enables the preparation of almost any pulp density attainable in a commercial plant. Heavy-hquid test work provides the basis for specifying the optimum screen size for the preparation of the feed. 

To size the two species however, it is necessary to separate them. A sink-float technique has been developed to separate the two. A carbon tetrachloride - tetrabromoethane mixture having an SG about 2.5 was used. The dry crystal mixture is added to the dense organic liquid, then put under vacuum to remove entrapped air bubbles. The suspension is then centrifuged for several hours to separate out the gypsum which floats and the hemihydrate which sinks. Tests on synthetic mixtures showed that a very clean separation is possible. 

Determination of the washability characteristics of coal by the float and sink (float-sink) method can be applied to coal of any particle size provided suitably large vessels to hold the larger lumps are available. Air-dried coal, not dry coal, should be used since the separation depends partly on the difference in specific gravity of the clean coal and dirt particles, and the specific gravity, in turn, is dependent on the moisture content of the coal. If the coal is dried before the test is carried out, the conditions will then differ from those in commercial washers, and the results will be at variance with those obtained in practice. 

ASTM C729-75 el (1995), Standard Test Method for Density of Glass by the Sink-Float Comparator, American Society for Testing and Materials, Philadelphia, PA. 

We have studied V and Ni transport in two catalyst blends. The first blend contained 75 wt.% ECAT with 2400 ppm V and 2400 ppm Ni blended with 25 wt.% Davison RV4+ metals trap [4].The second blend contained 75 wt.% of a commercial lab-deactivated catalyst impregnated with 4900 ppm V by Davison s CPS deactivation procedure [2], mixed with 25 wt.% lab-deactivated Davison metals trap (RV4+). These catalyst blends were tested at various reactor temperatures (675-750°C), catalyst average residence times in the reactor (14 -120 min), amounts of excess oxygen (0 to 3%), and steam levels in the reactor feed (0 to 30%). Samples of 20 - 40 g of catalyst were collected and separated by the sink-float method. 

The sink-float method requires a beaker, pipette, burette and two liquids. The liquids must be miscible and inert to the fiber being tested. One liquid must be less dense than the fiber and the other liquid must be more dense. A known volume of liquid A is pipetted into a beaker and the fiber is immersed in the liquid. The second liquid, B, is then added dropwise from a burette to the beaker with constant stirring. As the density of the liquid solution in the beaker changes, a point is reached where the density of the liquid precisely equals that of the fiber and the fiber will neither sink nor float but will remain suspended in the liquids. The volume of the second liquid added to the beaker is recorded and the density of the fiber is calculated ... 

Test procedures for density (specific gravity) determinations are commonly too imprecise, that is, have too much of an error margin, to be employed for delicate studies of density distributions across WPCs. Those distribution charts would have been very useful for die design, for structural and functional analysis of WPC profiles, and for other research and development projects. However, by employing the sink/ float procedure for density determinations, we have been able to obtain density distribution diagrams, some examples of which are shown in Figures 6.2-69. It should be noted that the maximum density of GeoDeck WPC profiles is 1.24-1.25 g/cm. ... 

Sink-float methods are commonly used for quality control measurements for glasses. A sample is placed into a test tube containing an organic liquid which is slightly more dense than the sample. The tube is heated until the density of the liquid becomes less than that of the sample, whereupon the sample will begin to sink. If the test tube also contains a standard of known density, the difference in temperature at which the sample and standard sink can be used to calculate the difference in their densities, provided the temperature dependence of the density of the liquid is known. This method is capable of detecting differences in density of as little as 20 ppm. 

Prepare a saturated solution of sodium sulphide, preferably from the fused technical sodium polysulphide, and saturate it with sulphur the sulphur content should approximate to that of sodium tetrasulphide. To 50 ml. of the saturated sodium tetrasulphide solution contained in a 500 ml. round-bottomed flask provided with a reflux condenser, add 12 -5 ml. of ethylene dichloride, followed by 1 g. of magnesium oxide to act as catalyst. Heat the mixture until the ethylene dichloride commences to reflux and remove the flame. An exothermic reaction sets in and small particles of Thiokol are formed at the interface between the tetrasulphide solution and the ethylene chloride these float to the surface, agglomerate, and then sink to the bottom of the flask. Decant the hquid, and wash the sohd several times with water. Remove the Thiokol with forceps or tongs and test its rubber-like properties (stretching, etc.). 

Thus, the above results for the Upper Freeport coal indicate that density-based processes (e.g., float-sink separation) should be able to remove significant amounts of mineral matter, while surface-based processes (e.g., froth flotation) will likely be unable to reduce the mineral content significantly. Results of cleaning tests reported elsewhere [5] have generally verified these predictions. 

Solvent test - A small amount of powder is poured onto the surface of a liquid and its sinking or floating behavior is observed. Liquids of different polarities such as toluene, formamide, ethylene glycol, and water were used. 

A useful procedure for checking if test pieces lie within certain limits of density is to prepare two liquids of different but known densities to be within the known limits a test piece must sink in one liquid and float in the other. This can be employed, for example, to rapidly sort parts made in two materials which have been mixed up. A further variation6 is titration of a heavier liquid into a lighter liquid until the test piece just floats, as given in ISO 1183-16. 

I tested my tactile sensitivity. I worked my way back to the couch and found Alice. My exploration of the softness of the sweater and the warmth of her flesh was an ecstatic sensual experience. However, it was devoid of sexuality, devoid of passion. While on the couch, the stimulation of touch became less important to me as I began to experience the dichotomous sensation of sinking into the cushions and yet floating slightly above them. 

Leaf discs have commonly been used for bioassays to determine if herbicides inhibit photosynthesis (Table 16.2). The simplest leaf-disc bioassay uses small discs cut from fully expanded cucumber or pumpkin cotyledons, floated in the light on a phosphate buffered medium containing suspected photosynthesis inhibitors.115 Qualitatively, if photosynthesis is inhibited, the leaf disc sinks. There are several variations of this method that can provide quantitative data. Evolution of O2 in the test solution can be measured with an oxygen electrode, CO2 induced pH changes colorimetrically determined with bromothymol-blue, or electrolyte leakage monitored with a conductivity meter. Leaf strips, algae, isolated chloroplasts, and duckweed (Lemna minor) have been used as test subjects. Although the bioassays presented in Table 16.2 are fairly easy to perform, few allelochemicals have been tested as possible inhibitors of photosynthesis. Many... 

Select a piece of plastic and add it to liquid 1. If it does not sink, push it under the surface with the forceps to make certain that trapped air bubbles are not keeping it afloat. Note whether it is more or less dense than the liquid. If it sinks in liquid 1, test the sample with liquid 2. Repeat until the sample floats in one of the liquids. Write down the approximate density of this sample based on your observations. Similarly test the other samples that you are provided and record your results. If you know the identity of these samples, compare your results with the data in Table 1 on the next page. If you are given an unknown plastic, deduce its possible composition using the data in Table 1. 

The amount of vitamin B12 in the serum sample is determined as follows. The amount of radioactive [ Co]cobalamin bound to the beads is measured. The purpose of using the beads is to facilitate the separation of bound P CoJcobalamin from the nonbound [ Co]cobalamin remaining in solution (floating around versus sinking to the bottom of the test tube). High levels of bound radioactivity indicate that the scrum sample contains low vitamin levels. Low levels of bound radioactivity indicate that the scrum contains high levels of vitamin. Plasma folate is... 

Pharmacopeias require that hard capsules be tested in the same apparatus as tablets even though they have very different physical properties. Filled capsules contain entrapped air, and most formulations will float on water. Devices are required to ensure that they sink, and these can influence the results obtained. Gelatin and hypromellose are adhesive materials and tend to block wire meshes that form part of the standard equipment. The way in which capsules disintegrate and dissolve is dependent upon several factors such... 

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